Here is the short answer: build a base mix of equal parts peat moss (or coco coir), aeration, and compost or vermicompost, then add about 2 to 3 cups of mineral and meal amendments per cubic foot. Wet it, let it sit for 4 to 8 weeks, and plant into it. After that you mostly just add water. Super soil is a one-time feed built into the pot, not a bottle schedule.
organic cannabis super soil recipe
Why the ratios matter more than the brand names
People get hung up on which kelp meal or rock dust to buy. The bigger factor is balance. Too much nitrogen input and you get a hot mix that curls leaves. Too little mineral content and the plant stalls in week five of flower. I aim for roughly one third peat, one third drainage, one third biologically active compost, then amendments that cover nitrogen, phosphorus, potassium, calcium, magnesium, and trace minerals.
Best Super Soil Recipe for Cannabis: Comparison Review
Compost does the heavy lifting. Soil organic matter holds water and nutrients and gives microbes a place to live, which is the whole point of this approach. If your compost is weak, no amendment list will save the mix.
Cannabis Super Soil Recipe: Step by Step
The recipe, measured per cubic foot
One cubic foot is about 7.5 gallons. Scale up by multiplying, and mix on a tarp.
- Base: 1/3 sphagnum peat moss or coco coir
- Base: 1/3 aeration (perlite, pumice, or rice hulls)
- Base: 1/3 compost and vermicompost, about half and half
- 1/2 cup kelp meal
- 1/2 cup neem meal or karanja meal
- 1/2 cup alfalfa meal
- 1/2 cup crustacean meal (crab or shrimp shell)
- 1/2 cup fish bone meal or steamed bone meal
- 1/2 cup feather meal
- 1 cup soft rock phosphate
- 1 cup basalt or glacial rock dust
- 1/2 cup gypsum
- 1/2 cup oyster shell flour
- 1/4 cup Epsom salt
- Optional: 1 cup charged biochar, 1/2 cup langbeinite in place of some rock dust
What each amendment is doing
Feather meal and alfalfa feed the nitrogen cycle slowly. Bone meal and rock phosphate cover phosphorus for flower. Kelp brings potassium plus growth hormones and trace elements. Crustacean and oyster shell meals are calcium sources that also feed chitin-loving microbes. Gypsum adds calcium and sulfur without shifting pH. Rock dust is your broad-spectrum mineral shot. Neem meal is partly nitrogen and partly pest pressure control in the root zone. None of these are optional in my book except the biochar.
Cooking the mix
Moisten the whole pile to the feel of a wrung-out sponge. Cover it with a tarp and keep it somewhere between 60 and 80 degrees Fahrenheit. Turn it once a week so it stays aerobic. Four weeks is the floor. Eight weeks is safer, especially if your compost was young. The finished mix should smell earthy and sweet. A sour or sewage smell means it went anaerobic and needs turning and drying.
Planting into super soil
Do not fill a pot with this stuff and drop a seedling in. Layer it. Put super soil in the bottom 50 to 60 percent of the pot and plain base mix on top. Roots grow down into the rich layer as the plant gets bigger and hungrier. For clones and seedlings, use even less, maybe a quarter of the pot. Mature transplants can take a 50/50 split.
Watering and pH
Water slowly, keep the mix evenly moist, and skip the flush. Runoff testing on organic soil tells you very little because the mix buffers itself. A tap water pH between 6.5 and 7.5 is fine for most people. If your water is very hard, cut it with rain or filtered water rather than pouring pH down into a living soil.
Mistakes I see most
- Doubling the amendments for a stronger mix. More is not better, it is hotter.
- Skipping the cook and planting into raw meal.
- Using fresh manure instead of finished compost.
- Letting pots dry out completely, which kills the biology you paid for.
- Adding bloom boosters on top of an already complete mix.
One legal note: rules on growing cannabis and hemp vary by state and country. Check your local regulations before you mix a batch.